<select name="{$field.name}" id="{$field.name}" class="form-control" {$field.extra_attr|default=''}>
    {present name="field.options.none"}{notempty name="field.options.none"}<option value=''>{$field.options.none}</option>{/notempty}{php}unset($field['options']['none']);{/php}{else/}<option value=''>请选择 {$field.title|default=""}</option>{/present}
    {foreach name="field.options" item="option" key="option_key"}
        {php}if(is_array($option)):{/php}
            <option value="{$option_key}" {present name="field.value"}{eq name="field.value" value="$option_key"} selected{/eq}{/present}
                {foreach name="option" item="option2" key="option_key2"}
                    {$option_key2}="{$option2}"
                {/foreach}>
                {$option.title}
            </option>
        {php}else:{/php}
            <option value="{$option_key}" {present name="field.value"}{eq name="field.value" value="$option_key"} selected{/eq}{/present}>{$option}</option>
        {php}endif;{/php}
    {/foreach}
</select>